Because heuristic search is often useful. For example, I was recently running some searches for Final Fantasy 10, and was highly appreciative of Google also finding pages where 10 was written as X.
Of course, heuristic features in computer programs usually benefit from a "do what I say, not what I mean" override option, but it's reasonable to call that an advanced feature.
The problem is that Google frequently gets it wrong. A typical example: I was searching for a party's view of "wind turbines", and the second or third result was an article about that party's political "power" struggles. Bolded. Because wind turbine = power.
Of course, heuristic features in computer programs usually benefit from a "do what I say, not what I mean" override option, but it's reasonable to call that an advanced feature.